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Test Drive: Sterling LNG Tractor

T. Boone Pickens, the billionaire investor and big-time oilman, is hawking his "Pickens Plan" in TV commercials, personal appearances and a web site (www.pickensplan.com). He envisions the U.S. gaining energy independence by converting cars and trucks to burn domestically produced natural gas instead of gasoline and diesel fuel, and using more solar and wind energy to make electricity. This will help reduce the need to import oil at huge cost from countries whose people don't like us. Pickens has invested heavily in natural gas and wind power, which means, "I'm putting my money where my mouth is," as he says.

Even the Sierra Club backs the Pickens Plan because of its emphasis on "clean" energy. Natural gas burns so nicely that it's being boosted by government agencies, which are offering hefty subsidies to help operators buy and operate vehicles that use it. Some of those are going to work at the Ports of Los Angeles and Long Beach, in sunny but sometimes smoggy southern California, where port authorities are cracking down on old, smokey tractors that have been hauling cargo containers from and to shipside yards.

Among the new vehicles are 165 Sterling L-113 tractors with Cummins-Westport ISL-G engines - diesels built to burn natural gas. Daimler Trucks North America officially delivered them to a for-hire fleet at a ceremony in early December. These are the type of truck that Pickens talks about, because they return to their home terminal every day for refueling at specialized stations. To cram enough gas aboard, natural gas can be compressed or, in this case, liquefied through super cooling and carried in a special saddle tank, giving a tractor a range of 250 to 300 miles - not as far as an over-the-road diesel, but enough for this operation.

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Cummins-Westport, a joint venture between Cummins Inc. and Westport Innovations, has several gas-fired engine models, including this ISL-G, which uses advanced stochiometric combustion, cooled exhaust-gas recirculation, and a three-way catalyst to lower emissions to 2010 levels. This version makes 320 horsepower and 1,000 pounds-feet. That's not monstrous, but the ISL's displacement is only 8.9 liters or 544 cubic inches. Yet it's as strong or stronger than a typical early 1970s Cummins NH or NTC, a bulky 14-liter (855-cubic-inch) diesel that weighed about 900 pounds more. (In those days, 250 was considered "plenty of power" by old-timers who remembered earlier 150- and 180-horse motors.)

Here at the Port of Long Beach, Daimler set up some of the new tractors for qualified trade press reporters to drive, and I piled into one of 'em to see how it goes. The Sterling is called a Setback 113 for its setback steer axle and its bumper-to-back-of-cab length in inches. California's bridge formula law is close to the federal B formula, and they both encourage a forward-set front axle, but an axle-back arrangement works because the tractor's wheelbase is a longish (for a daycab) 178 inches. And a tight wheel cut allowed by the axle-back configuration aids maneuverability.

The tractor was hitched to a stout container chassis carrying a moderately loaded 40-foot steel box. Gross weight was only about 52,000 pounds, and for that the 320-horsepower engine was entirely adequate. Our hosts had mapped out a route on nearby streets and freeways that are typical of where these vehicles travel. Intersections near the port were controlled by traffic signals set to blink red in all directions instead of the usual green-amber-red cycles. Heavy trucks accelerate slowly and traffic would back up if the normal cycles were used.

It'd be different if all the tractors prowling the area had Allison automatic transmissions, as these Sterlings do. Daimler produced a video showing a rig like this out-dragging another with a bigger engine but a manual transmission, and it's true as far as it went, which was maybe 45 mph. All I had to do was step on the accelerator and steer, and we scooted smartly through these intersections. The Allison sent continuous power through the driveline while other drivers had to pause multiple times to upshift. An Allison ain't cheap, but it allows a truck and driver to do more work, and meanwhile the driver can relax and keep his mind on where the rig is.

Higher road speeds, however, require more horsepower, and on freeways the smallish ISL had to work hard. Also, it was somewhat gear bound: The Allison has overdrive 5th and 6th gears, but the rear axle ratio on this tractor was a short 6.14 to 1, so we got to 55 and 60 mph, but not much beyond. While doing 65 on short downhills the engine was spinning close to its 2,000-rpm limit. Then again, this tractor and its brothers will stay in the L.A. Basin where traffic is heavy much of the time and 55 is the legal limit anyway. Besides, probably half of its trips will be with empty containers where less power is needed.

Gaseous fuels can cause a converted diesel to make a bawing sound, but this engine sounds more like a diesel. And it runs smoothly no matter where the tachometer needle points. This engine made a strange, steady chirping sound above 20 mph or so, and Daimler people didn't know why. It wasn't annoying or noisy because the Sterling was quiet overall. It was comfortable, as well, with roomy cab dimensions, a good air-ride seat, well-padded ceiling and door panels, and an attractively laid-out instrument panel. Outward visibility was excellent in all directions and the tractor rode well over sometimes rough concrete. This would be a nice place to spend a work day (or night), I thought.

Both inside and outside, Sterlings strongly resemble the fine-driving Ford L-series heavies from which they are descended. It's a shame that the trucks and the brand have to go away this month, but Daimler executives felt forced by tough times to make a tough decision. They pointed out that the same powertrain package is now optional on Freightliner Business Class M2-112 tractors, which are nice-driving vehicles, too.

Cummins-Westport engines are also available from Kenworth and Peterbilt in models that, like those from Freightliner, are well suited to a variety of local hauling jobs where natural gas is on tap. To be sure, the special equipment makes such trucks expensive: Each of the Sterlings costs about $160,000. But $90,000 of that is paid for by grants from federal, state and local sources, according to Chung Liu of the South Coast Air Quality Management District, one of the enthusiastic backers of the concept. Other grants are available for the costly LNG fueling stations needed by these tractors.

Natural gas itself is likewise favored by government bodies through reduced taxation. That and its abundance in many parts of the U.S. make its cost per British Thermal Unit considerably less than diesel fuel, said Chris Patterson, Daimler Trucks' president and CEO.

These tractors are "part of the solution" to pollution, said Bob Curry Sr., president of Cal Cartage, the fleet acquiring them. Everybody at the ceremony agreed that by cleansing the air around the ports, natural gas will improve the health of workers and neighbors.

The gas-fired engines burn so cleanly that they don't need particulate filters to meet current diesel exhaust emissions limits. And they already meet 2010 standards. That along with the subsidies make these trucks and this fuel an increasingly appealing proposition, whether or not you agree with T. Boone Pickens.